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Dealing with Bugs and Disease
The roses we offer in our catalog
are tough, yet beautiful plants. However, you're not going to be
the only one who likes them. There will be days when you go out
to the garden and cry, "what's been eating my roses?!" Or "what's
wrong with my roses--they have spots on the leaves!" What to do?
First, don't panic! Second, find out what's causing the damage before
you get out the sprayer and the poisons. Remember, the key to dealing
with problems is finding out what is causing them first. Then, you
can work on fixing what's wrong.
of the hardy roses we sell are relatively disease resistant or tolerant
and don't need chemical sprays. However, if conditions are right,
blackspot and mildew can become a problem on some plants. And, if
you have a lot of roses, you'll want to control these diseases before
they spread to other plants. Blackspot and powdery mildew are spread
by spores that require specific temperature, moisture and humidity
conditions to spread. Generally, these diseases are the worst in
early summer and early fall when temperatures at night are cool
and moisture or humidity is high.
prevention and control: Keep your roses healthy by watering
them consistently and adequately, preferably in the morning so the
leaves have a chance to dry off in the morning sun. Providing the
right amount of nutrients through fertilizer or compost also keeps
your roses healthy. A healthy rose is less susceptible to disease.
Good housekeeping practices help to reduce the spread of diseases.
Disease spores can overwinter on dead leaves and reinfect new growth
the following spring. To prevent this, pick-up dead leaves in the
fall or spring and burn or dispose of them. Or, cover the leaves
each spring with a new two-inch blanket of mulch to prevent the
spores from spreading. Also remove and burn or dispose of dead canes
In addition to the above, you have three choices for controlling
blackspot and powdery mildew:
- Tolerate some blemishes on your roses, and do nothing. However,
remember that if a rose looses too many leaves, the plant will
become weakened and may eventually die. The disease will also
then become established in your garden and may spread to other
- Establish a routine spraying program using commercially available
fungicides labeled for roses, such as Funginex (Triforine) or
Daconil 2787. Spray your susceptible varieties every 7 to 10 days
starting in early spring. Be absolutely sure to follow the instructions
on the containers, and wear goggles and a respirator to protect
your eyes and lungs! Remember that for most sprays to be effective,
they must be applied every 7 to 10 days throughout the growing
- Use "organic" sprays. As with choice #2, you must follow a regular
spraying schedule (every 7 to 10 days throughout the growing season)
to prevent the disease problems from occurring. These sprays can
also be used after the disease first appears to prevent it from
spreading. However, unlike option #2, organic materials are less
hazardous to human health and the environment, with the exception
of fungal diseases.
Organic disease control can be achieved using commercially-available
fungicides containing sulfur, copper or Neem, which are very
effective against many leaf spot diseases. To find these products,
check out our sources for supplies at
the bottom of this page. Or, make your own spray using a mixture
developed and proven effective by Cornell University's Plant
Pathology Department. Add one tablespoon of baking soda and
2½ tablespoons of Sunspray ultrafine horticultural oil per gallon
of water. Mix well and apply in the early morning or late evening.
Be sure to follow this recipe, since higher concentrations of
both baking soda and horticultural oil can cause leaf damage.
This recipe is very effective against powdery mildew.
If you don't feel confident about this method, or any other
sprays, you may want to test your spray mixture on a small part
of your rose plant before you completely spray the plant to
make sure there are no phytotoxic reactions (leaf drop).
Important Note: Use caution before you spray rugosa roses! Most
rugosas are "allergic" to chemical sprays; some sprays will cause
their leaves to yellow and fall off. Fortunately, most Rugosas are
completely disease resistant and don't need to be sprayed. However,
there are a few exceptions. If your rugosa is exhibiting signs of
blackspot, it's probably because its breeding includes a nonrugosa
variety that is susceptible to blackspot. Test your spray on a part
of the plant and if it doesn't drop its leaves, go ahead and spray
the whole plant if you see blackspot.
The common insects that attack roses are aphids, cane borers,
Japanese beetles and sawfly larvae. Over time, you can observe the
life cycles of insects that are common in your area. You'll begin
to recognize just when certain insects appear and become a problem
for your roses. This kind of observation is very important for minimizing
the amount of insect control you have to do, and the amount of pesticides
you use -- organic or not. Using pesticides, even organic ones,
disrupts the natural cycle of predator and prey in the insect world.
Therefore, you want to be sure not to kill the "good" insects --
the ones that eat the ones you don't like. Here are some guidelines
- Know your enemy! Know what it is and understand its lifecycle.
Maybe you only need to spray once instead of spraying all summer
"just in case..."
- Before killing off the pest, if possible, wait a few days to
see if a natural predator can control them for you. For example,
in the early summer, lady bugs seem to come out of nowhere and
eat all the aphids in our garden. However, for the second flush
of aphids that show up in late summer, I need to release lady
bugs to control the pests.
- Spray or dust when the pollinators are NOT collecting nectar,
such as in the early evening (at dusk).
- Follow up each application of pesticides with another application
a few days later if the pest is still around. This is especially
effective for controlling aphids.
- Ask yourself if you're willing to tolerate the pest. Don't flip
out the first time you see a bug on your roses. Bugs are part
of the natural world and can be quite interesting if you have
an open mind about it. Find out if you can tolerate what it might
be doing to your roses (again figure that out first before you
kill it). If not, then you know what to do.
Remember, all pesticides -- organic or not -- are designed to kill
a pest. Therefore, they can't be good for your lungs, eyes, skin,
etc. Wear protection! Goggles, respirator, longsleeved pants and
To control aphids, use insecticidal soap, or spray them off the
plants with water from a hose. Another way to control aphids is
to buy good bugs that eat the aphids. We release lady bugs every
4 to 5 days in our gardens starting in late May. They provide almost
100% control of aphids in early summer. We have to release lady
bugs again starting in mid July through August to keep the late
summer aphid populations down, which are a bit tougher to control.
Cane borers: If the tips of your rose canes wilt, then you
probably have cane borers. Look for a hole on the cane where the
borer entered and cut back the cane until you find the culprit,
and then squish it. You may want to cover the cut with vaseline
to prevent diseases from entering the wound.
Stem Borers (Agrilus aurichalceus): The adult
beetles lay eggs in rose canes and their larvae eat their way around
the diameter of the cane causing it to swell -- usually in a 1-
or 2-inch area on the lower part of the cane. The top of the cane
above the swollen section usually dies. In addition, the swollen
section readily breaks off in the wind or if you move it around.
Cut the infected cane back to the ground, and cover the cut with
or elmers glue. Dispose of the infected cane to prevent the larvae
from surviving, maturing and eventually laying eggs in other canes.
It's important to remove infected canes as soon as you notice a
problem to prevent it from spreading. In some areas, Rugosas seem
to be most susceptible to stem borers.
beetles: Use powdered rotenone or pyrethrum-based insecticides
to kill Japanese beetles. Another method is to kill the beetle larvae
using biological controls such as beneficial nematodes or a product
called "milky spore." A new Neem-based product is available that
repels the beetles. Or, manually knock them off your roses into
a jar filled with water and kill them. Or trap them with specially
designed Japanese Beetle traps that use a pheremone to attract them.
Rose Chafers: These pests are usually only a problem in
areas with sandy soils. They also only seem to be a problem in early
summer. Control methods are similar to Japanese Beetles. Use powdered
rotenone or pyrethrum-based insecticides to kill Chafers. Another
method is to kill the chafer larvae using biological controls such
as beneficial nematodes or a product called "milky spore." A new
Neem-based product is available that repels the chafers. Or, manually
knock them off your roses into a jar filled with water and kill
them. Or trap them with a specially designed Rose Chafer trap that
uses a pheremone to attract them.
larvae: Sawfly larvae (or rose slugs) are a bit harder to control
since they remain on the undersides of leaves where they are hard
to reach with spray. Sawfly larvae are small (½-inch long) green
worms that are easy to identify because they tend to wrap themselves
in a tight circle.
For organic control, shake the plant and step on the worms as
they fall on the ground (this can be either repulsive or very gratifying),
or spray them with Bioneem™ or insecticidal soap. Again, be sure
to follow the instructions and precautions listed on the containers.
Another control method is provided by birds; specifically, wrens.
Place wren houses around your rose garden and watch the birds do
the work! Wrens are very tolerant of human activity and they relish
sawfly larvae. Wrens can raise up to three clutches per summer;
consequently, they never stop hunting for food. The birds may not
provide 100 percent control, but they help tremendously, and add
to the enjoyment of your garden through their wonderful songs.
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